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Control of the direction of motion is an essential feature of biological rotary motors and results from the intrinsic chirality of the amino acids from which the motors are made. In synthetic autonomous light-driven rotary motors, point chirality is transferred to helical chirality, and this governs their unidirectional rotation. However, achieving directional rotary motion in an achiral molecular system in an autonomous fashion remains a fundamental challenge. Here, we report an achiral molecular motor in which the presence of a pseudo-asymmetric carbon atom proved to be sufficient for exclusive autonomous disrotary motion of two appended rotor moieties. Isomerization around the two double bonds enables both rotors to move in the same direction with respect to their surroundings-like wheels on an axle-demonstrating that autonomous unidirectional rotary motion can be achieved in a symmetric system. [ABSTRACT FROM AUTHOR]

We investigate the hitherto unexplained wave which inundated the village of Dwarskersbos, South Africa, in the early hours of August 27, 1969, in the absence of any seismic disturbance or major meteorological storm. A field survey, based on the interview of nine elderly witnesses still residing in the community, documented maximum run-up of 2.9 m, concentrated on an extremely short segment of coastline, less than 2 km in length. These characteristics are incompatible with generation by a seismic source (which, at any rate, should have been felt by the population). A landslide source, located at the only canyon featuring a steep enough ocean floor, is also ruled out since a numerical simulation fails to reproduce the concentration of the wave at Dwarskersbos. By contrast, the wave can be explained as a 'meteo-tsunami' resulting from resonance between a meteorological squall propagating at 18 m/s in the azimuth $$\hbox {N101}^{\circ }\hbox {E}$$ and a gravity wave propagating in the shallow waters off the eastern shore of St. Helena Bay. This is confirmed by numerical simulation under the formalism of Proudman (Dynamical oceanography. Methuen, London, ), which provides a satisfactory model of the distribution of run-up along the beach. [ABSTRACT FROM AUTHOR]

The coat protein (CP) gene of 75 South African Potato virus Y (PVY) isolates was amplified using reverse-transcriptase polymerase chain reaction (RT-PCR). The resulting cDNA products were cloned and sequenced. These sequences were used to identify the strains to which the isolates belonged. Some, when compared to reference sequences, belonged to the PVYN and PVYO strains. A number of isolates were found to demonstrate significant homology to PVYN strains from China. A large number of South African isolates possessed CP sequences showing evidence of recombination between PVYN and PVYO strains, similar to those of PVYNTN isolates. Multiplex RT-PCR analysis allowed further differentiation of PVYO isolates and revealed that the majority were of the PVYN-Wilga strain. It was deduced that the most likely way in which these isolates reached South Africa was via the importation of infected material. [ABSTRACT FROM AUTHOR]

Resulting from the 21st UN Climate Change Conference (COP21) in Paris in 2015, the European Union's (EU) current climate and energy objective is to reduce greenhouse gas (GHG) emissions by 40% below 1990 levels by 2030, and transportation must play a vital role in achieving this target. Decarbonization is therefore one of the main challenges for the freight transport sector in Europe. Several measures are suggested to contribute to this goal, including clean vehicle technologies, optimising networks and modal shift. This paper focuses on the latter measure; specifically, we reveal the value of shift-share analysis as a method for assessing a freight modal shift's contribution to carbon dioxide (CO2) emission reduction. The shift-share method is in fact a decomposition analysis that originated in the field of regional economics. However, it can also be applied in other fields, including transport economics. We have exploited this method's broad applicability to develop a tool that can evaluate how rail and inland waterway transport perform in terms of their contributions to CO2 emission reduction due to a modal shift. In demonstrating the tool, we analyse the market for freight transport that has the Netherlands as an origin, destination or both, thereby distinguishing between five distance markets. The goal of this paper is to present and show the value of the tool. The tool can provide policy makers with background information about the changes in CO2 emissions of a freight transport modal shift that occurred in the past, which in turn can be helpful in devising future transport policies. A particular strength of the tool is that it can be used on any spatial scale - countries, regions, corridors, etc. In addition, the data requirements and computing complexity of the shift-share method is low. [ABSTRACT FROM AUTHOR]